1. Field of the Invention
This invention relates to a digital-to-analog converter suitable for use in, for example, a digital audio device.
In a signal reproduction circuit of a digital audio device such as a compact disc player, a digital signal reproduced from a recording medium is converted into an analog signal. In such a case, since the digital reproduction signal generally takes the form of a binary fixed-point number, a digital-to-analog converter (hereinafter referred to as "D/A converter") of the type in which all bits of the digital reproduction signal are directly supplied to a weighted register network or an R-2R resistor ladder network is generally used.
As is well known, one of the most important features of a digital audio device is the reproducibility of a small signal with less distortion. It is also well known that distortion contained in the output signal of a D/A converter of this type increases with the decrease of magnitude of the input data. And therefore, for example, when it is desired to reproduce a signal at a level of -60 dB (full-scale level is 0 dB) with a distortion less than 1%, the D/A converter must have such a high accuracy that a signal at a level of 0 dB can be reproduced with a distortion less than 0.001%, which accuracy is equivalent to fifteen to sixteen bits. However, it is extremely difficult to improve the accuracy of a D/A converter of this type to such an extent.